Bleeding air from gas turbine engine gas paths, including from compressors, is well known. Air bled from the compressor can be used to provide a source of pressurized and/or cool air to the engine or the aircraft, however air is principally bled from the compressor in order to improve the operating envelope and overall compressor efficiency, which is often expressed as improved surge margin. Bleed flow from other areas of a turbo machine gas path can be used for purposes of component cooling, pressurizing air/oil seals, providing cabin air, performance/operability improvement, and the like.
In a compressor, low momentum flow along the outer shroud of the compressor is known to be detrimental to the aerodynamic performance or to trigger premature rotor stall. Accordingly, bleeding such low momentum air flow at the shroud is performed to improve engine performance and operability. Bleeding air from the compressor shroud can be done in a number of ways, for example using bleed holes or continuous slots formed in the shroud.
Improved shroud bleed hole configurations are however sought.